Re: Spin down HDD after disk sync or before power off

On Sun, Mar 08, 2009 at 01:36:09PM +0100, Bernd Walter wrote:
On Fri, Mar 06, 2009 at 03:47:38PM -0600, Rick C. Petty wrote:
On Fri, Mar 06, 2009 at 03:30:14PM -0600, Octavian Covalschi wrote:
Why is spinning down is bad for HDD ? I believe it's better to spindown a
drive,
instead of cutting power too sudden.

Comparing those two, I'd say it shouldn't matter (although probably a
forced spindown may be better). But pulling power from a drive does not
mean the drive immediately stops doing stuff.

My understanding is that without power the heads just slamm into
landing zone, while it can be done in a controlled smooth way with
power.

Nope, according to a coworker (whose wife works for an HDD manufacturer),
the spindle motor is shunted and the generated electricity is used to
properly land the head. My coworker also tells me that some new drives are
actually parking the heads off the disk, which as I understand is a much
more difficult task since you have to worry about vertical separation when
you bring the heads back between the platters.

I was just saying spindown on disks is bad in the first place. Sure, you
might save some wear and tear on the bearings, but you risk problems with
the heads on both spindown and spinup. In other words, if you can avoid
power-cycling your drives, they should last longer (in that you're less
likely to destroy the heads).

This depends on the disks.
Desktop and especially mobile drives are designed to sustain more
spin downs, but are not designed for rotating a long time.
But of course if you intend to spin up directly after spin down it
might be bad for them as well, since it isn't really saving spinning
time.

That may be; I know nothing about differences with mobile drives. If this
is true, I'd like to find some replacement 2.5" drives which are intended
for continuous spinning.

This is nothing, which should be done on reboot, but for halts it
might be reasonable to do.

Not sure what you're trying to say here, but I am for the idea of
issuing a spindown request if we know the power is to be cycled. If
spindown are issued for all halts, I hope someone makes that a kernel
tunable.

What I was hoping is that someone could point me to the "spinup" command as
I have a drive which does not spin up until it receives this command. Any
takers?

-- Rick C. Petty
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